The ability to select hybridoma cells secreting an antibody of choice without resorting to cumbersome screening techniques would greatly decrease the time involved in obtaining those cells. We have perfected a method which uses fluoresceinated anti-idiotypic antibody to identify those hybridoma cells making antibody of a specified idiotype. These cells are identified and cloned by the cell sorter in a one step procedure, greatly reducing the effort needed to obtain hybridomas of choice.